1. Technical Field
The illustrative embodiments relate to a swing-type display device, and more particularly to a swing-type display device incorporating a linear array of a plurality of light-emitting elements, such that each light-emitting element is activated for a predetermined period with a predetermined luminance level as the device itself is swung by a user, whereby an image is displayed in the trajectory of the swing due to persistence of vision.
2. Description of Background Art
Swing-type display devices incorporating an array of plurality of red LEDs (Light Emitting Diodes) are known. As the swing-type display device is swung, the red LEDs flicker with a predetermined pattern, whereby text characters (e.g., “STOP”) appear to be formed in the air due to persistence of vision.
However, conventional swing-type display devices, which display images based on flickering red LEDs, can only display text characters or simple diagrams. There is also a problem in that the displayed image may contain stripes associated with the interspaces between the red LEDs.
Therefore, a feature of the illustrative embodiments is to provide a swing-type display device which is capable of displaying images in various colors. Another feature of the illustrative embodiments is to provide a swing-type display device in which the problem of the displayed image containing stripes associated with the interspaces between the light-emitting elements is alleviated.
The illustrative embodiments have the following aspects to attain the features mentioned above. Note that reference numerals and the like are added between parentheses in the below description only for the purpose of facilitating the understanding of the present invention in relation to the below-described embodiments, rather than limiting the scope of the invention in any way.
A swing-type display device according to the illustrative embodiments comprises first light-emitting elements (10R) capable of emitting light in a predetermined color, second light-emitting elements (10G) capable of emitting light in a color which is different from the predetermined color, and a control section (51). A linear array of the first light-emitting elements extends in a direction substantially perpendicular to the direction of the swing. The first light-emitting elements and the second light-emitting elements are arranged in pairs of two, such that each second light-emitting element is disposed near a corresponding one of the first light-emitting elements. The control section activates each of the first and second light-emitting elements for a predetermined period (T) to emit light in a luminance level in accordance with image data. Thus, when the swing-type display device is swung, an image corresponding to the image data is displayed in the trajectory of the swing. Thus, by employing at least two kinds of light-emitting elements emitting light of different colors from one another, it becomes possible to display images in various colors, beyond the capabilities of conventional swing-type display devices. By employing three kinds of light-emitting elements emitting light of different colors from one another, it becomes possible to display images in even more colors than in the case of employing two kinds of light-emitting elements. Note that the image data may include data representing text characters.
Typically, the predetermined period is equal to a period for displaying a single pixel of the image. Thus, lines (e.g., lines 1 to 8 in FIG. 6) constituting the image are consecutively displayed in the trajectory of the swing motion of the swing-type display device, so that the entire image appears in the trajectory of the swing due to persistence of vision.
Preferably, the first and second light-emitting elements of each pair are located side by side in the direction of the swing (FIG. 1). Thus, the trajectory of the first light-emitting elements and the trajectory of the second light-emitting elements when the swing-type display device is swung coincide with each other, thereby enabling proper displaying of the image. Furthermore, the control section may control one of the first and second light-emitting elements of each pair that is located more to a rear along the direction of the swing of the swing-type display device to be activated a predetermined time (Δt in FIG. 15B) later than the other light-emitting element which is located more to a front along the direction of the swing of the swing-type display device. Thus, it is ensured that the position at which a first light-emitting element is activated to display a given pixel coincides with the position at which a corresponding second light-emitting element is activated to display the same pixel, thereby enabling proper displaying of the image. Such a structure is effective in the case where the first and second light-emitting elements constituting each pair are widely spaced apart, or where the light-emitting elements are mounted on the swing-type display device without any covering means thereon.
The tilt sensor may further comprise an optical guide (20) for allowing the light emitted from the first and second light-emitting elements to propagate therethrough to outside of the swing-type display device. Preferably, the optical guide includes a face, oriented toward the outside of the swing-type display device, which is matte-finished to diffuse the light propagating through the optical guide (FIG. 2A). Thus, the light from the first and second light-emitting elements of each pair is adequately diffused, thereby rendering the stripes appearing in the displayed image due to the interspaces between the light-emitting elements less conspicuous (FIG. 3B). Preferably, a groove (201) is formed on the first face of the optical guide, in a position opposing each of boundaries between adjacent pairs of first and second light-emitting elements. Thus, the light output from a given pair of light-emitting elements can be prevented from propagating through the optical guide to the neighborhood of another pair of light-emitting elements.
The control section may drive each of the first and second light-emitting elements for the predetermined period by PWM technique using a pulse having a frequency based on the image data ((a1) to (a3) of FIG. 12). By using a pulse whose frequency takes at least two values in accordance with the image data, not only are the light-emitting elements activated or deactivated, but the luminance of the activated light-emitting elements is varied in accordance with the image data, thereby enabling a display in a greater variation of colors. Alternatively, the control section may drive each of the first and second light-emitting elements for the predetermined period with a current or voltage based on the image data ((b1) to (b3) in FIG. 12). In this case, too, by using a current or voltage which can take two values in accordance with the image data, the luminance of the activated light-emitting elements is varied in accordance with the image data, thereby enabling a display in a greater variation of colors.
The swing-type display device may further comprise a tilt sensor (30) for detecting a tilt of the swing-type display device, the tilt sensor including a ball (301) which is capable of reciprocating between a first position (FIG. 4A) and a second position (FIG. 4B) in synchronization with the swing of the swing-type display device. The control section may begin activating each of the first and second light-emitting elements each time the ball is moved out of the first (FIG. 8A) or second position (FIG. 9A). Thus, an image can be displayed at an appropriate position in the trajectory of the swing by using a simple structure.
Another swing-type display device according to the illustrative embodiments comprises: a linear array of light-emitting elements, the linear array extending in a direction substantially perpendicular to the direction of the swing, a control section (51), partitions (80), and a covering member (70) composed of a light-transmitting material. The control section activates each of the light-emitting elements for a predetermined period to emit light in a luminance level in accordance with image data. Each partition is disposed between light-emitting elements, thereby restricting the directions in which the light output from the light-emitting surfaces of the light-emitting elements can travel. With such partitions, it is possible to adjust the regions of the covering member which is struck by the light. The covering member is provided to cover the light-emitting elements and the partitions, the covering member being composed of a light-transmitting material. A plurality of convex portions (701) are formed on the covering member, each shaped as a ridge extending along the direction of the swing. The convex portions refract the light from the light-emitting elements (which are point sources) so as to exit the covering member. As a result, a uniform luminance can be obtained within the light-outgoing surface of the covering member (i.e., the face of the covering member via which light goes out) while minimizing the decrease in luminance. As a result, pixel-to-pixel stripes can be made hardly noticeable.
Preferably, the convex portion has a lenticular-lens-like or wedge-like configuration (as shown at 701 in FIG. 20). By forming such convex portions, it becomes possible to obtain an even more uniform luminance within the light-outgoing surface of the covering member (see FIGS. 19A, 19B and 20).
A plurality of said partitions may be formed in a light-emitting area on the second face which is attributable to each of the light-emitting elements. By forming the convex portions in such positions, the colors of adjoining pixels are adequately intermixed by the action of the convex portions present between pixels, thereby enabling a more thorough elimination of stripes (see FIGS. 19A, 19B, 20, and 21C).
A plurality of convex portions (701) may be formed in a light-emitting area on the face of the covering member which is attributable to each of the light-emitting elements, and the covering member may be disposed so as to leave a predetermined space from the partitions (80) (FIG. 19B). Thus, since the light output from the light-emitting elements overrides the partitions to an adequate extent, the stripes appearing in the displayed image due to the interspaces between the light-emitting elements are rendered even less conspicuous. Furthermore, the covering members may be formed at least on portions of the first face opposing the partitions. (see dotted lines in FIGS. 19B and 20). Thus, the light overriding the partitions is refracted so as to be output in a direction perpendicular to the light-emitting surfaces of the light-emitting elements, thereby rendering the stripes in the displayed image even less conspicuous.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.